siren output as horn

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=109871
Printed Date: July 15, 2025 at 12:23 PM

Topic: siren output as horn

Posted By: rikki_92
Subject: siren output as horn
Date Posted: December 19, 2008 at 7:26 AM

I have just installed a immobilizer to my 92 ford fairlane. I was wondering if i could use my horn on the siren output. The siren out put is a negative output with a pulse. How would i wire up the relay ? And i need to know if this ok to use on a 1amp ? The install manual says - ve siren output 1amp max.

Cheers rick

Replies:

Posted By: tedmond
Date Posted: December 19, 2008 at 4:47 PM

horn is a ver low current since it uses a factory relay to control the horn. do you know if the Horn trigger on the car is negative or positive?

most cars are negative but there are positive so make sure. post back and i will show you what to do.

Posted By: rikki_92
Date Posted: December 19, 2008 at 5:41 PM

Mate i think it's a negative setup. Because the metal plate in my steering wheel is pressed the horn will sound.

Posted By: tedmond
Date Posted: December 19, 2008 at 5:48 PM

hey rikki,

i would like you to test the wire with a multi meter or a volt meter so i can verify then show you. I dont want to tell you something then it causes damage to the car.

test the wire like so

determines if you have a negative horn.
with volt meter, set it to DC @ 20volts
RED probe to constant 12volts
BLACK probe to horn wire on car.
the volt meter should show 0 volts. when you press the horn, it should jump from 0 to 11-12.4volts

determines if you have 12v horn style
with volt meter, set it to DC @ 20volts
RED probe to horn wire on car
BLACK probe to Ground

the volt meter should show 0 volts. when you press the horn, it should jump from 0 to 11-12.4volts
this indicates you have a positve horn.

testing will take about 2 mintues of your time. very simple task.

Posted By: rikki_92
Date Posted: December 19, 2008 at 6:54 PM

Mate from the relay to the horn it's positive. if you want me to i can scan my horn wiring. Hopefully i did this right.

Cheers rick

Posted By: tedmond
Date Posted: December 19, 2008 at 11:07 PM

if you can upload, sure that would be great.

Posted By: rikki_92
Date Posted: December 19, 2008 at 11:47 PM

This picture is from the factory ford manual.

And from what i can tell i don't think the alarm has a pulse single.

Thanks for your help mate

Cheers Rick

Posted By: rikki_92
Date Posted: December 19, 2008 at 11:49 PM

Here is the picture of the horn relay >br> posted_image

Posted By: tedmond
Date Posted: December 20, 2008 at 9:17 PM

your horn is a positive system, however you need a NEGATIVE trigger to trigger the factor relay.

just take the output you have now if negative and wire it to the horn wire on the car.